Call processing monitor system

ABSTRACT

The present invention is a call processing monitor circuit for dynamically verifying the operation of a telephone switching center. This system provides for continuously testing a telephone switching center&#39;s ability to process telephone traffic. This is accomplished by placing telephone calls one at a time from various network inlets to various network outlets in the switching center. For the detection of a predetermined number of consecutive failures, an output alarm signal is generated by the system.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention pertains to the automated testing of a telephoneswitching center and more particularly to a call processing monitorsystem for continually initiating telephone calls and detecting whethereach call was properly completed.

(2) Description of the Prior Art

In present date telephony, switching systems are implemented withcomplex configurations of hardware and software elements. Such switchingsystems are computer controlled systems and many of such systems havemultiprocessor configurations. Each switching system has software whichmonitors various hardware operations and initiates alarms for thedetection of any faults. In a similar fashion, specialized hardware isimplemented in order to detect certain software faults.

It is of particular importance to detect those hardware and latentsoftware faults which affect the switching function of a telephoneswitching center. However, certain faults may go unrecognized or ifrecognized the system may be incapable of initiating the proper alarm.These faults may inhibit the processing of telephone calls for extendedperiods of time. Typically, modern switching centers are unattended forsubstantial periods of time. Thereby, faults which affect the callprocessing function of the switching center may go undetected. Suchswitching systems may include No. 1 EAX and No. 2 EAX manufactured byGTE Automatic Electric Inc.

Initially, methods of detecting a call processing service outageconsisted of an operator at another office being unable to complete acall to the service affected switching center or a customer who reportsthe switching center outage from another switching center. Such methodsare inadequate and thereby, a community may be without telephone servicefor an extended period of time.

A partial solution to the problem is taught by U.S. Pat. No. 4,021,624issued on May 3, 1977, to P. M. Kelly et al, which teaches an automaticcall generator which attempts to place calls from one dedicated spot toanother. This system employs complex logic and a central processing unitincluding 16 programs which operate this system.

Another complex solution is taught by U.S. Pat. No. 3,692,962 issued onSept. 19, 1972, to J. R. Raczynski et al, which teaches an array of upto 5 automatic dialing devices operating independent of one another andproducing a count of attempts and failures of each dialing device.

Two other systems which employ computer control for automatic callgeneration are taught in U.S. Pat. Nos. 3,952,172, issued on Apr. 20,1976, to C. J. L. Penn et al, and 3,692,961, issued on Sept. 19, 1972,to G. J. LeStrat et al.

Therefore, it is the object of the present invention to provide a callprocessing monitor system which monitors the call processing ability ofa switching center in a simple and economical fashion and provides analarm output when a particular threshold of consecutive failures isexceeded.

It is a feature of the present invention to provide the above mentionedobjective without a central processing unit and any operating softwarewhich itself may contain latent errors.

It is another feature of the present invention to provide aself-contained unit independent of the switching center to which it isconnected.

It is another feature of the present invention to provide alarm outputswhich may be transmitted to a remote location.

SUMMARY OF THE INVENTION

The present invention comprises a call processing monitor system for usein conjunction with a telephone switching center. The telephoneswitching center includes a plurality of originating and terminatinglines for connecting the call processing monitor system to the switchingcenter.

The call processing monitor system includes a relay network connected toeach of the originating lines (tip and ring pairs). Dial tone detectorsare connected to each of the originating tip and ring pairs andconnected to a selection circuit for controlling the telephone digitswhich are to be transmitted. A digit transmission circuit is connectedto the selection circuit for the transmission of all digits representingthe telephone number. A digit sequencing circuit is connected betweenthe selection circuit and the transmission circuit providing for theproper timing of the digits and the interval between digits.

Ringing detectors are connected to each of the terminating lines. Ananswer circuit is connected to each of the ringing detectors. A testtone generation circuit is also connected to the ringing detectors. Itprovides for the transmission of a tone of frequency 1000 Hz to theswitching center via the terminating line. A delay circuit is connectedto the test tone generation circuit and provides for proper timingbefore the test tone is supplied to the terminating line.

Test tone detectors are connected to each of the originating lines andprovide for the detection of the 1000 Hz frequency applied by the testtone generation circuit. A timing circuit is connected to each of thetest tone detectors and provides an indication of whether the attemptedtelephone call has been completed timely. Lastly, a programmablethreshold counter is connected between the timing circuit and an outputrelay latch.

When the circuit is initialized, the timing circuit begins to run andthe relay network is operated to select one of the originating lines onwhich to place a call for service to the switching center. Dial tone istransmitted by the switching center and detected by the dial tonedetector which is connected to the originating line. When this occurs,the selection circuit selects the first digit for transmission, thetransmission circuit outpulses the particular digit and the sequencingcircuit provides for proper timing until all the digits comprising thetelephone number have been transmitted. Based upon the telephone numbertransmitted, the switching center establishes a connection between theoriginating line and the particular terminating line which was dialed.The switching center then applies ringing current to the terminatingline. The ringing detector connected to the particular terminating linedetects the flow of ringing current and initiates the answer circuit toprovide ring trip to the switching center via the terminating line. Atthis point, there has been a connection established from the originatingline through the switching center to the terminating line.

After a 1/2 second the delay provided by the delay circuit, the testtone generation circuit applies a frequency of 1000 Hz to theterminating line. The test tone detector connected to originating linedetects this application of tone and provides a signal to the timingcircuit. If the test tone has been detected before the expiration oftiming circuit's interval, a successful call has been made through theswitching center. The timing circuit then reinitializes the system andprovides a successful indication of the completed call. If the timingcircuit has expired before the detection of the test tone, the timingcircuit provides an indication of a fault.

The threshold counter collects the indications provided by the timingcircuit. For a predetermined number of consecutive failures thethreshold counter provides an output signal which operates the relaylatch to provide a suitable remote or local alarm.

The system also provides the ability to check itself for properoperation. By manual switching, the selection circuit is inhibited fromoperation on any calls, thereby generating the required number ofconsecutive failures for operation of the threshold counter and latchingthe output relay for an alarm condition.

In addition the circuit provides for the manual selection of thetelephone numbers to be dialed, the kind of ringing scheme to bedetected, the overall timing of the timing circuit and the number ofdigits to be transmitted.

DESCRIPTION OF THE DRAWINGS

FIGS. 1-9, taken in combination, comprise a schematic diagram of a callprocessing monitor system embodying the principles of operation of thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention comprises a call processing monitor systemconnected between a number of originating and terminating lines of atelephone switching center. Referring to FIGS. 1 through 9, a momentarypushbutton switch master reset is shown connected to timer 101. Timer101 is connected to flip-flop 121 and flip-flop 121 is connected to ANDgates 112 and 114 which in turn are connected to relays CFS-1 and CFS-2respectively. Flip-flop 121 is connected to flip-flop 127 and toflip-flop 129 which in turn are connected to relays CN1 and CN2respectively.

Six originating lines connect the call processing monitor system to thetelephone switching center. Each of these lines comprises a tip and aring lead shown in FIG. 8. The first originating line is composed of tiplead T1 and ring lead R1; second line is composed of tip lead T2 andring lead R2, etc. Relays CFS-1, CFS-2, CN1 and CN2 operate to select ona sequential basis one of the originating lines to generate a call forservice to the switching center. Dial tone detectors 305 and 307 of FIG.8 are connected between the switching center and OR gate 119 of FIG. 1.OR gate 119 is connected to flip-flop 120. Timer 101 is also connectedto digit select counter 124 and counter 124 is connected to digit selectdecoder 125. Digit select decoder 125 and AND gates 142 and 143 areconnected to the telephone digit storage array 308 which is shown inFIG. 9. Digit storage array 308 is connected to dial pulse counter 201shown in FIG. 3. Dial pulse counter 201 is connected to NOR gate 137 ofFIG. 1 through monostable 202.

Oscillator 219 of FIG. 5 is connected to counter 131 of FIG. 1.Flip-flop composed of NOR gates 135 and 136 is connected to call forservice relays CFS-1 and CFS-2 and operate the relay which initiated thetelephone call.

Two terminating lines connect the call processing monitor system to thetelephone switching center. These two terminating lines are composed oftip lead PT7 and ring lead PR7 and tip lead PT8 and ring lead PR8 shownin FIG. 8. Ringing detectors 302 and 303 are connected to theseterminating lines. Ringing detector 302 is connected through flip-flop206 of FIG. 2 to answer relay AR1 and in similar fashion ringingdetector 303 is connected through flip-flop 211 to answer relay AR2shown in FIG. 2. The contacts associated with answer relays AR1 and AR2are shown in FIG. 8 connected between the tip and ring leads of theterminating lines.

The test tone generator shown in FIG. 7 is composed of amplifier 216 andinductor 217 and capacitor 218 and is connected between counter 132shown in FIG. 1 and each of the terminating lines shown via contactsTTC1 and TTC2 in FIG. 8. Test tone detectors 304 and 306 of FIG. 8 areconnected between the originating lines and OR gate 118 of FIG. 1. ORgate 118 is connected to monostable 111 which is connected to failurethreshold counter 204 of FIG. 4 through NAND gate 126 via the ALMRSTlead shown in FIG. 1. Timer 102 is connected to monostable 103 which inturn is connected to the threshold counter 204 via the ALMCLK lead. InFIG. 4 switches 205 are connected between threshold counter 204 andrelay MJA. The contacts of relay MJA are shown in FIG. 6 and areconnected to lamp indicators or to a remote location for manualindication to an attendant.

In FIG. 1, timers 101 and 102 may be implemented via an integratedcircuit part number NE555 manufactured by Signetics Incorporated.Monostables 103, 111, 208, 209, 213 and 214 may be implemented with anintegrated circuit part number MC14528 manufactured by MotorolaIncorporated. Digit select counter 124 may be implemented via anintegrated circuit part number MC14526 manufactured by MotorolaIncorporated. Digit select decoder 125 includes an integrated circuitpart number CD4028 manufactured by Radio Corporation of AmericaIncorporated. Counters 131 through 134 of FIG. 1 and 204 shown in FIG. 4may be implemented with integrated circuit part number MC14017manufactured by Motorola Incorporated.

In FIG. 3 dial pulse counter 201 may be implemented via integratedcircuit part number MC14526 manufactured by Motorola Incorporated. Dialpulse delay monostable 202 includes an integrated circuit part numberMC14528 manufactured by Motorola Incorporated. In FIG. 5 oscillator 219may be implemented via integrated circuit part number NE555 manufacturedby Signetics Incorporated. In FIG. 7, operational amplifier 216 may beimplemented via integrated circuit part number 1458 manufactured bySignetics Incorporated. In FIG. 8, tone detectors 304 through 307 may beimplemented via integrated circuit part number NE567 manufactured bySignetics Incorporated. Ring detectors 302 and 303 include an opticalcoupler device part number OPI-1083 manufactured by SpectronicsIncorporated.

Referring to FIG. 1, when momentary pushbutton master reset is operatedthe call processing monitor circuit is initialized and all counters andlatches reset. Originating line comprising tip lead T1 and ring lead R1of FIG. 8 is selected first and the other tip and ring lead pairs areselected sequentially. The call processing monitor system will determinewhether a successful call can be completed by the telephone switchingcenter to a terminating line comprising tip lead PT7 and ring lead PR7.In response to master reset initialization, timer 101 times a 30 secondinterval between successive call attempts by the call processing monitorsystem. Upon the expiration of timer 101, timer 102 is initiated. Timer102 is an overall time-out timer measuring the total time allowed forcompletion of the call. A switchable input to timer 102 determineswhether a 56 second or a 112 second interval is selected.

When timer 102 is activated a signal is produced and transmitted throughinverter 109 which represents an off-hook indication on the selectedoriginating line. This off-hook signal is then gated through AND gate112 or 114 to operate relay CFS-1 or CFS-2 respectively, depending uponwhich originating line in the sequence was selected. In addition, theexpiration of timer 101 causes the first digit of the called directorynumber to be retrieved via the operation of digit select counter 124 anddigit select decoder 125. An indication is transmitted from decoder 125to the appropriate set of switches in the digit storage array 308 ofFIG. 9. The value of the particular digit selected is then transmittedfrom storage array 308 to dial pulse counter 201 of FIG. 3.

When dial tone is detected by tone detector 305 or 307 of FIG. 8, anindication is transmitted to OR gate 119 of FIG. 1 and the dial pulsegenerating circuit comprising counters 131 through 134 is enabled. Theproper number of dial pulses representing the selected digit are thentransmitted to the switching center via the particular originating line.These pulses are generated via the dial pulse generator comprisingcounters 131 through 134 and the operation of flip-flop comprising NORgates 135 and 136. Each pulse that is transmitted also produces a signalwhich is transmitted from NOR gate 136 to dial pulse counter 201 of FIG.3. When dial pulse counter 201 is counted down to zero the digit hasbeen transmitted and monostable 202 is initiated which provides for a570 MS. delay before retrieving the next digit from the storage array308 of FIG. 9. At the end of the time interval, monostable 202 has itsoutput go high, thereby causing the next digit value to be loaded intodial pulse counter 201 and enabling the dial pulse generator to transmitthis digit. When the last digit to be transmitted has been determined bydial pulse counter 124 (value representing the number of digits isselectable via switches), an output is generated by decoder 125 whichresets the dial pulse enable flip-flop 120.

In response to the dialed digits, the telephone switching center willconnect a path from the originating line to the particular terminatingline which was called. Ringing current supplied by the switching centerwill be detected by ringing detector 302 or 303 of FIG. 8. Thisindication is transmitted via the RCS1 or RCS2 lead to flip-flop 206 or211 respectively of FIG. 2. Answer relay AR1 or AR2 is operated whichprovides ring trip to the switching center. In addition, the setting offlip-flop 206 or 211 initiates monostable 208 or 213 to provide a 500Ms. time interval. At the expiration of this interval, test tone connectrelay TTC1 or TTC2 is operated to connect a 1000 Hz. frequency to theterminating line. This frequency is generated by oscillator 219 of FIG.5 having its output counted down by counters 131 and 132 of FIG. 1. Thisoutput is then transmitted to amplifier 216 of FIG. 7 through inductor217 and capacitor 218 to the selected terminating line of FIG. 8.

The test tone is transmitted through the switching center's connectionto the originating line. Test tone detector 304 or 306 detects theapplication of this tone and provides an indication which is transmittedto OR gate 118 of FIG. 1. In response to the detection of the test tonemonostable 111 is initiated which provides for a 3.8 millisecond timinginterval. Monostable 111 resets the overall timer 102 and in response amonostable 103 is initiated which provides a 2 millisecond timinginterval.

As a result, a logic "0" is generated and transmitted via the ALMCLKlead to threshold counter 204 and the counter is not advanced. Counter204 is reset via a signal generated by gate 126 of FIG. 1. Switches 205of FIG. 4 may be set to a predetermined value from one to six, so thatrelay MJA is operated for detection of a consecutive failure count ofthe value set via the closing of one of the switches 205. Relay MNAwhose corresponding contacts are shown in FIG. 6.

Additionally, the selection circuitry is operated so that the next tipand ring pair are selected for placing the telephone call.

If test tone is not detected by tone detectors 304 or 306 the expirationof overall timer 102 causes a logic "1" to be generated and transmittedvia the ALMCLK lead to counter 204. When the predetermined thresholdcount is achieved by the proper number of consecutive failures, relayMJA is operated. Test select switch comprising contacts 116 and 117 maybe operated to inhibit the selection circuitry gates 112 and 114 fromoperating on a consecutive basis. Thereby, the consecutive thresholdcount is reached and relay MJA is operated.

Manual selection of a particular ringing scheme may be accomplished viaswitches 301 of FIG. 8. The overall timing interval for call completionis selectable via a switch connected to timer 102 shown in FIG. 1. Thenumber of digits to be transmitted by the call processing monitor systemis selectable via switches connected to counter 124. The particulartelephone numbers to be called are selectable via switch array 308 ofFIG. 9. The consecutive failure threshold limit may be set via switches205 of FIg. 4. All the above mentioned switches may be implemented viadual in line package switches in order to conserve space.

Contacts MJA shown in FIG. 6 may be connected to operate a lamp locatedwithin the telephone switching center or connected to a transmissionline to operate a remotely located lamp or other suitable device.

Although a preferred embodiment of the invention has been illustrated,and that form described in detail, it will be readily apparent to thoseskilled in the art that various modifications may be made thereinwithout departing from the spirit of the invention or from the scope ofthe appended claims.

What is claimed is:
 1. A call processing monitor system for dynamicallyverifying the operation of a telephone switching center includinginitialization means, a plurality of originating lines each connected tosaid switching center and a plurality of terminating lines eachconnected to said switching center, said call processing monitor systemcomprising:means for selecting one of a plurality of said originatinglines, said selecting means operated in response to said initializationmeans; dial tone detection means connected to each of said plurality oforiginating lines and operated to detect application of dial tone bysaid switching center; second means for selecting digit valuesrepresenting a telephone directory number operated in response to saidoperation of said dial tone detection means; means for transmitting saiddigit values connected to said second selecting means; means forsequencing said digit values for transmission connected to saidtransmission means; ring detection means connected to said terminatingline and operated to detect a complete path from said originating lineto said terminating line through said switching center; answer meansconnected to said ring detection means and operated in response to saidoperation of said ring detection means to produce a signal representingan off-hook condition; test tone generation means connected to saidanswer means and operated in response to said off-hook condition toproduce a test tone of a particular frequency; delay means connected tosaid answer means and operated in response to said off-hook condition toconnect said generated test tone to said terminating line; test tonedetection means connected to said originating line for detection of saidcomplete path through such switching center whereby a first outputsignal is produced representing the detection of said complete path;timing means connected to said initialization means and to said testtone detection means, said timing means operate to time a predeterminedinterval whereby upon expiration of said interval a second output signalof a first characteristic is produced and alternatively for detection ofsaid test tone a second output signal of a second characteristic isproduced; threshold counting means connected to said timing means andoperated in response to a plurality of second output signals of a saidfirst characteristic to detect a consecutive accumulation of said secondoutput signals whereby a third output signal is produced representingsaid consecutive accumulation attaining a predetermined threshold limit;and latching means connected to said threshold counting means andoperated in response to said third output signal to produce a fourthoutput signal representing an indication of consecutive failures of saidcall processing monitor system.
 2. A call processing monitor system asclaimed in claim 1, wherein: said threshold counting means includesmanually programmable memory means which contains said threshold limitvalue N where N is an integer value representing a predeterminedthreshold limit.
 3. A call processing monitor system as claimed in claim1, wherein: said timing means includes switching means whereby at leasttwo distinct timing intervals are manually selectable.
 4. A callprocessing monitor system as claimed in claim 1, wherein: said secondselecting means includes fully programmable memory means whereby anytelephone directory number is selectable.
 5. A call processing monitorsystem as claimed in claim 1, wherein: there is further includedroutining means connected to said initialization means and operated toinhibit the operation of said first selection means whereby saidthreshold limit of said consecutive failures is produced and said fourthoutput signal generated.
 6. A call processing monitor system as claimedin claim 1, wherein: said first selecting means includes switching meansfor sequentially selecting each of said plurality of originating lines.7. A call processing monitor system as claimed in claim 1, wherein: saidsecond selecting means further includes switching means for sequentiallyselecting each of said plurality of terminating lines corresponding to atelephone directory number.
 8. A call processing monitor system asclaimed in claim 1, wherein: said second selecting means furtherincludes dial pulse generating means connected between said secondselecting means and one of said plurality of said originating lines fortransmitting a series of pulses representing each of said digits of saidtelephone directory number.
 9. A call processing monitor system asclaimed in claim 8, wherein there is further included: a clock circuitconnected to said test tone generation means and to said dial pulsegenerating means.
 10. A call processing monitor system as claimed inclaim 1, wherein: said ring detection means includes a plurality of ringdetection circuits, each circuit connected to a particular terminatingline and each including an optical coupler device.